In a network, such as a telecommunications network, the asynchronous delivery of digital data is essentially distinguished from a synchronous service in that the response to a request may be temporarily stored on a dedicated server on the network before being sent to a client station.
The temporary storage of the response makes it possible to alleviate poor or limited connectivity of the client station or of a server having the resource or data requested.
Different methods and devices for asynchronous delivery of data are known in the state of the art.
Thus, document U.S. Pat. No. 6,070,184 describes a service for asynchronous delivery of data for a Web browser installed on a mobile apparatus such as a PDA or GSM telephone.
The client Web browser of the mobile apparatus connects itself temporarily or intermittently to a dedicated server on the Internet network. The function of the dedicated server is to relay a command received from the mobile apparatus to a remote server on the Internet network, to receive and store the response of the remote server and to inform the client Web browser of the availability of the response.
The development these last few years of distributed networks and systems of “peer-to-peer” (or P2P) type has favored the appearance of services for asynchronous delivery, in particular for digital images.
This is because, in P2P networks and systems, the client stations and the servers connect and disconnect periodically to the network. The direct availability of the data on the network is very random. The temporary storage of the images requested and their deferred delivery constitute a technical solution adapted to P2P technology.
Thus a system of P2P type for sharing multi-resolution digital images is known to the inventors in which original images at high resolution remain stored on local servers of the users (client machines) of the system. Low resolution versions of the images on the other hand are stored on a central server of the system and are directly available for the users. A certain quality of service is obtained by the availability on the central server of the low resolution versions of the images. However, a problem of availability remains for the original images, especially when the connectivity of the local servers holding these original images fluctuates or when the reproduction quality of the original images is low.
In order to solve this problem of availability of the original images at high resolution, it has been proposed to include a dedicated server for the original images in the above image sharing system. Deferred downloading of the original images is made onto the dedicated server from the client machines holding the images. The dedicated server next warns the requesting users of the availability of the original high resolution images.
Although the methods and devices for asynchronous delivery of digital data of the prior art described above have given satisfactory technical solutions at the time of their design, those methods and devices today merit being improved.
Thus, a point on which the prior art calls for improvement is the manner in which the responses to the requests of users are provided to them.
This is because the responses are provided to the users as raw information and the users experience some difficulty in associating the responses received with the requests sometimes made considerably earlier. For example, the users' machines may be in very different operating states on receipt of the responses, with respect to the states at the time of making the corresponding requests.
Another desirable improvement of the prior art concerns the processing reserved for successive requests from the same user.
When no specific processing has been planned, each of the requests is processed independently of the others, and the user receives the same number of response notifications as requests made. Thus, for example, if the user makes the same request twice by error, he will receive two response notifications even though a single one would suffice. Apart for the lack of user-friendliness, these multiple notifications generate additional traffic on the network which it would be desirable to reduce to a minimum.
The asynchronous delivery service according to U.S. Pat. No. 6,070,184 does offer a possibility of stringing together or grouping together of the responses according to preferences expressed by the user beforehand, but this solution is not satisfactory in all cases. This is because it requires a deliberate intervention by the user. Furthermore, the grouping together carried out is static, and no change is possible without further intervention by the user.